Upgrading of middle distillates with coordinated complexes



Nov. 5, 1963 E. R. QUIRAM 3,109,367

UPGRADING 0F MIDDLE DISTILLATES WITH COORDINATED COMPLEXES Filed Sept. 14. 1960 COORDINATED MIDDLE DISTILLAT'E Mp FEED c0 LEX 2, H

CONTACTING MIDDLE DISTILLATE 3 RAFFINATE SEPARATING BI'CYCLIC AROMATIC sq EXTRACT AROMATIC EXTRACT RECOVERY 4" VINYL 1 PYRIDINE REACTIVATI N6 Ernest R. Quirum Inventor BY WLMW Patent Attorney United States Patent 3,109,867 UPGRADING 0F MIDDLE DISTILLATES WITH COORDINATED C(BMiLEXES Ernest R. Quiram, Elizabeth, NJ, assignor to Esso Research and Engineering Company, a corporation of Delaware Filed Sept. 14, 1960, Ser. No. 56,005 6 Claims. (Cl. 259- 674) The present invention concerns a process for the extraction of undesirable aromatic hydrocarbon compounds from petroleum middle distillates. More particularly, the present invention concerns a process for upgrading middle distillate petroleum fractions whereby the undesirable aromatic hydrocarbon compounds are selectively extracted from said petroleum fraction. In its specific aspects, the present invention concerns a process whereby a middle distillate petroleum fraction is upgraded by contacting the petroleum fraction with a coordinated complex which selectively extracts the bi-cyclic aromatic hydrocarbon compounds, leaving an upgraded middle distillate raftinate.

Middle distillates, such as kerosene and jet fuel, are upgraded by removing the aromatic hydrocarbon compounds from them. There are aromatic extraction processes (S0 and furfural) available for the upgrading of middle distillates. However, with both S0 and furfural, the extraction phase relationships are such that a closed extraction diagram exists. As a result, pure aromatics cannot be produced with a simple extraction. Furthermore, since furfural boils within the boiling range of middle distillates (i.e., 162 C. as opposed to a 120260 C. cut), the solvent recovery system is quite complicated.

It is desirable to extract essentially pure aromatics since any incidental removal of parafiins and naphthenes tends to degrade the fuel. Furthermore, an essentially pure aromatic stream is a good feedstock for a hydrogenation process in which the aromatics are hydrogenated to naphthenes which are then blended back into the raffin-ate from the extraction process.

In a paper presented to the American Chemical Society (Philadelphia section) Symposium on High Energy Fuels at Philadelphia, Pennsylvania, on February 25, 1960, by W. G. Dukek, entitled Selected Hydrocarbons as High Performance Fuels, it is pointed out (page 4) that carbon deposits in a supersonic jet engine are controlled by the concentration of heavy aromatics in the fuel burned.

On page 6 of the above paper, it is shown why naphthenes, particularly multi-ring naphthenes, give better performance in jet fuels than their corresponding aromatic compounds. Again, on page 15, the desirability of naphthenic jet fuels is pointed out. a

Table I sets out the luminometer number of several hydrocarbon compounds. The luminometer number of a fuel indicates its carbon forming tendency upon combustion. The by-cyclic aromatic compound, methyl naphthalene, has a very low luminometer number, and hence the desirability of removing bi-cyclic aromatic compounds from kerosene or jet fuel is apparent.

3,199,857 Patented Nov. 5, 1963 "Ice Therefore, it is an object of the present invention to provide a process for the selective removal of aromatics, and particularly the bi-cyclic aromatics such as naphthalenes, from middle distillate petroleum fractions.

In accordance with the present invention, this is accomplished by contacting a middle distillate petroleum fraction with a coordinated complex which selectively takes up the bi-cyclic aromatic compounds in the middle distillate, leaving a middle distillate raifinate.

The mixed base coordinated complexes, which are a part of the present invention and have been found to have a high selectivity for naphthalenes, are Ni(4-ethyl pyridine) 2 (4-vinyl pyridine) (SCN) and N-i(4-methyl pyridine) (4-vinyl pyridine (SCN) It is known to the art to use a coordinated complex to separate compounds in the kerosene or lube oil boiling range. However, the complexes known to the art are all similar in that their composition includes only one basic nitrogen compound. Thus, it is known to use a complex such as Ni(4-methyl pyridine), (SCN) to separate aromatic hydrocarbon mixtures in the kerosene boiling range. It is, therefore, an object of the present invention to provide a coordinated complex having two basic nitrogen compounds with a selectivity for the extraction of naphthalenes from middle distillates far greater than coordi nated complexes known to the art.

It is a further object of this invention to provide a means for reactivating a coordinated complex when the composition of the complex includes two basic nitrogen compounds.

The present invention may be more fully understood and its objects more fully appreciated by referring to FIGURE 1 which schematically depicts the process of the present invention.

The feed, line 1, which is a middle distillate petroleum fraction, and which has a boiling range, for instance, of from -260 C., is contacted with one of the mixed base coordinated complexes previously mentioned, such as Ni(4-ethyl pyridine) (4-vinyl pyridine) (SCN) line 2.

The contacting occurs at a temperature in the range of from 15 to 30 C. Higher temperatures may be used, i.e., 30 to 50 C., although a temperature in the range of from 15 to 30 C. is preferred.

Since the process is a liquid phase extraction, the operating pressure is not controlling and, thus, need not limit the process.

The amount of coordinated complex, line 2, contacted with the feed, line 1, depends on the quantity of aromatics extracted, the temperature at which the contacting occurs and the efiiciency of the contacting. Thus, the amount of coordinated complex, line 2, contacted with the feed, line 1, is 1 to 10 moles of complex per mole of the aromatic hydrocarbon compounds extracted from the feed, line 1.

Upon contacting the feed, line 1, with the coordinated complex, line 2, there is formed a middle distillate raffinate, and a predominantly bi-cyclic aromatic extract clathrated in the coordinated complex.

These two phases, line 3, are then separated by any suitable means, such as settling, centrifugal separating or filtering.

Upon separation, a middle distillate raflinate, line 4, is removed as the desired product.

The predominantly bi-cyclic aromatic extract, clathrated in the coordinated complex, line 5, is then heated to drive the aromatic extract, line 6, from the deactivated coordinated complex, line 7.

Since temperature eifects the equilibrium for the cla-thration of aromatic hydrocarbons, any increase in temperature tends to liberate the aromatic hydrocarbons from the coordinated complex.

Therefore, by heating the aromatic extract clathrated in the coordinated complex, line 5, to a temperature in the range of from 90 to 300 C. for a period of time in the range of from minutes to 3 hours, the predominantly bi-cyclic aromatic extract, line 6, is liberated from the deactivated coordinated complex, line 7. It is preferred to heat the aromatic extract in the coordinated complex to a temperature sufficient to vaporize the arcmatic extract. This considerably simplifies the separation of the aromatic extract from the deactivated complex. In the event the aromatic extract, line 6, is in the liquid phase, suitable separation means, such as filtering or centrifugal separating, may be used.

The pressure at which the heating step takes place is not of importance except insofar as it determines whether the liberated aromatic extract, line 6, is in the liquid or vapor phase. This consideration will, of course, determine the technique by which the aromatic extract, line 6, is separated from the deactivated complex, line '7.

7 Upon heating the coordinated complex to the temperature range indicated, the complex loses its ability to take up aromatics and is thus deactivated. This deactivation is accompanied by a loss of one of the basic nitrogen compounds in the complex. For instance, upon heating Ni(4-ethyl pyridine) l-vinyl pyridine) (SCN) some of the 4-vinyl pyridine is driven from the complex. Therefore, to restore the activity of the complex to its original selectivity, it is necessary to add to the deactivated complex the basic nitrogen compound that was driven oif in the heating step. In the preceding case, 4-vinyl pyri- V dine is added to restore the complex to its original selectivity.

Similarly, with Ni(4-methyl pyridine) (4-vinyl pyridine) (SCN) 4-vinyl pyridine is added.

The basic nitrogen compound that is driven from the complex along with the aromatic extract, line 6, during heating may be removed from the aromatic extract by Washing the aromatic extract with about a 1:1 solution of aqueous hydrochloric acid. The base passes into the acid solution which is readily separated from the arcmatic hydrocarbon compounds.

It should be noted that there are means other than heating for removing the aromatic extract, line 6, from the coordinated complex, line 7. By washing the arcmatic extract clathrated in the coordinated complex, line 5, with a dilute aqueous hydrochloric acid solution, the complex is destroyed and the aromatic extract, line 6, is liberated. However, the disadvantage of using the acid wash technique is that the coordinated complex cannot be readily recovered from the acid.

Therefore, heating the aromatic extract in the coordinated complex is the preferred method of liberating the aromatic extract, line 6, and obtaining a deactivated complex, line 7.

The deactivated complex, line 7, is then cooled and contacted with the basic nitrogen compound which has been driven from the complex in the heating step to reactivate the complex. In this case, 4-vinyl pyridine, line 8, is added to the deactivated complex, line 7.

. The amount of 4-vinyl pyridine added is in the range of from 0.1 to 5 moles of base per mole of complex. It is preferred to add about 2 moles of base per mole of complex to assure complete reactivation of the deactivated complex, line 7. Excess base may be removed from the coordinated complex by any suitable means, such as filtering or centrifugal separating.

g amass? Table II AROMATIGS EXTRACTION USING Ni l-EP) 1(4-VP) 2(5 ON) 2 Feed Extract Component Composition, Composition,

Wt. percent Wt. percent Benzene 0. 2 Toluene 0.3 l. 3 0. 9 4.1 3. 7 3. O 1.1 1. 7 0. 6 1.0 1.8 0. 7 1. 5 0. 3 0. 1 Naphthalenes 4. 6 84. 2 Indans 3.0 0.7

Total Aromatics 20. 2 94. 6 Total Naphthenes- 29.6 1. 6 Total Parafiins 37. 2 2. 9 Total 00nd. Naphthenes 13.0 0.9

Total- 100. 0 100. 0

The data of Tables II and III illustrate the selectivity of the coordinated complexes of the present invention for aromatic hydrocarbon compounds, specifically naphthalenes.

The data in Table II were obtained using Ni(4-ethyl pyridine) (4-vinyl pyridine) (SCN) as the coordinated complex.

The data in Table III were obtained using Ni(4- methyl pyridine) (4-vinyl pyridine) (SCN) The data of Tables II and III were obtained using the following technique:

Ten grams of freshly made coordinated complex were shaken with ml. of the feed, of the composition indicated, for 15 minutes at a temperature of 24 C. The slurry was .then filtered through filter paper using a Biichner funnel. The coordinated complex was then washed with a light solvent (n-hexane) to remove excess feed from the crystals. The coordinated complex was again filtered to remove excess light solvent. The coordinated complex crystals were decomposed with 100 ml. of a 1:1 aqueous hydrochloric acid solution. The hydrocarbons released from the coordinated complex crystals being immiscible in the acid solution, remained as a separate phase. The hydrocanbon phase was 'recovered and analyzed using a mass spectrometer.

In Tables II and HI, the names of the coordinated complexes are abbreviated. For instance, Ni(4-ethyl pyridine) (4viny1 pyridine) (SCN) is indicated by Ni(4-EP) (4-VP) (SCN) The data in Tables II and III indicate the high selectivity of the mixed base coordinated complexes of the present invention. These data show that Ni(4-ethyl .pyn'dine) (4-vinyl pyridine) (SCN) is the more selec- Table III AROMATICS EXTRACTION USING niti-rvrrna-vrhtsomi The mixed coordinated complexes used in obtaining the data in Tables 11 and III were prepared using the following technique.

In preparing Ni(4- ethyl pyridine) (4 -vinyl pyridine) (SCN) the starting complex was Ni(4-ethyl pyridine) (SCN) which was heated in an oven for 64 hours at a temperature of 121 C. to drive off 2 moles of 4- ethyl pyridine. To the dry di-coordinated complex, Ni(4-ethyl pyridine) (SCN) was added 2 moles of 4- vinyl pyridine. The result was the mixed crystal, Ni(4- ethyl pyridine) 2 (4-vinyl pyridine) 2 SCN) In preparing Ni(4 -methy1 pyridine) (4-vinyl pyridine) (SCN) Ni(4-methyl pyridine) (SCN) was heated for 23 hours at 140 C. to drive off 2 moles of 4-methyl pyridine. To the resultant complex was then added 2 moles of 4-vinyl pyridine to obtain the mixed coordinated complex, Ni(4 methyl pyridine) (4 vinyl pyridine) (SCN) Having described the present invention, what is sought to be protected by Letters Patent is set forth in the following claims.

What is claimed is:

1. An improved process for extracting bi-cyclic aromatic hydrocarbon compounds from a middle distillate petroleum fraction, which comprises contacting said middle distillate petroleum fraction with a coordinated complex to form a middle distillate rafiinate and a predominantly bi-cyclic aromatic extract clathrated in said coordinated complex, said coordinated complex being selected from the class of complexes comprising Ni(4-ethyl pyridine) (4-vinyl pyridine) (SCN) and Ni(4-methyl pyridine) (4-v-inyl pyridine) (SCN) and separating said middle distillate railinate from said predominantly bicyclic aromatic extract clathrated in said coordinated complex.

2. The process of claim 1 wherein said predominantly bi-cyclic aromatic extract is removed from said coordinated complex.

3. The process of claim 2 wherein said coordinated complex is reactivated by adding 4-vinyl pyridine to said complex, and contacted with said middle distillate petroleum fractions.

4. An improved process for extracting bi-cyclic aromatic hydrocarbon compounds from a middle distillate petroleum fraction, which comprises contacting said middle distillate petroleum fraction with a coordinated complex at a temperature in the range of from 15 to C. to form a middle distillate raffinate and a predominantly bi-cyclic aromatic extract clathrated in said coordinated complex, the amount of said coordinated complex contacted with said middle distillate being in the range of from 1 to 10 moles of complex per mole of aromatic hydrocarbon compounds extracted from said middle distillate, said coordinated complex being selected from the class of complexes comprising Ni(4-ethyl pyridine) (4-vinyl pyridine) (SCN) and Ni(4-methyl pyridine) (4-vinyl pyridine) (SCN) and separating said middle distillate rafiinate from said predominantly bicyclic aromatic extract in said coordinated complex.

5. The process of claim 4 wherein said predominantly bi-cyclic aromatic extract is recovered from said coordinated complex by heating said predominantly bi-cyclic aromatic extract clathrated in said coordinated complex to a temperature in the range of from to 300 C. for a period of time of from 10 minutes to 3 hours.

6. The process of claim 5 wherein said coordinated complex is reactivated by adding 4-vinyl pyridine in an amount of from 0.1 to 5 moles of 4 -vinyl pyridine per mole of complex, and contacted with said middle distillate petroleum fraction.

References Cited in the file of this patent UNITED STATES PATENTS 2,849,511 Schaeir'er et a1 Aug. 26, 1958 

4. AN IMPROVED PROCESS FOR EXTRACTING BI-CYCLIC AROMATIC HYDROCARBON COMPOUNDS FROM A MIDDLE DISTILATE PETROLEUM FRACTION, WHICH COMPRISES CONTACTING SAID MIDDLE DISTILLATE PETROLEUM FREACXTIN WITH A COORDINATED COMPLEX AT A TEMPERATURE IN THE RANGE OF FROM 15 TO 50* C. TO FORM A MIDDLE DISTILLATGE RAFFINATE AND A PREDO/MI-NANTLY BI-CYCLIC AROMATIC EXTRACT CLATHRATED IN SAID COORDINATED COMPLEX, THE AMOUNT OF SAID COORDINATED COMPLEX CONTACTED WITH SAID MIDDLE DISTILLATE BEING IN THE RANGE OF FROM 1 TO 10 MOLES OF COMPLEX PER MOLE OF AROMATIC HYDROCARBON COMPOUNDS EXTRACTED FROM SAID MIDDLE DISTILLATE, SAID COORDINATED COMPLEX BEING SELECTED FROM THE CLASS OF COMPLEXES COMPRISING NI(4-ETHYL PYRIDINE)2(4-VINYL PYRIDINE)2(SCN)2 AND NI(4-METHYL PYRIDINE)2(4-VINYL PYRIDINE)2(SCN)2, AND SEPARATING SAID MIDDLE DISTILLATE RAFFINATE FROM SAID PREDOMINANTLY BICYCLIC AROMATIC EXTRACT IN SAID COORDINATED COMPLEX. 